On his way to work, the student witnessed a traffic accident. his heart rate increased and his mental alertness improved as he assisted the victims. the student's response resulted from the release of:

During the past few weeks or months, have you noticed any exercises that have become too easy for you? do you think you need to increase the intensity in any of the three exercise areas in your workouts? evaluate your exercise progress in the three exercise areas (cardiovascular, resistance, and flexibility) and list what modifications, if any, you may need to make in your exercise routine.